Methods: Two small interfering RNA sequences targeting VDR were designed by online screening and were cloned into the expression vector(pSilencer-2.1-U6). Then the products,pSilencer-2.1-U6-VDR1 and pSilencer-2.1-U6-VDR2,were separately transfected into a human osteosarcoma cell line(HOS-8603) by liposome.

The tumor cell cycle of human osteosarcoma cell line OS-732 was studied by autor-adiography. Experimental result showed that the cell cycle time TC was 18. 7 h, mean mitotic index was 37.3%. TS, TM, TG2 and TG1 was 13.1 h, 1 h, 1 h, and 3.5 h respectively. Mean labelling index was 35.96%. Growth index was 51.34%. This result suggested that OS-732 maintains its growth characteristic and is a ideal cell line to study human osteosarcoma experimentally.

Marked hypercalcemia would be caused by ectodermic solid tumor remote from the bone and Without any indication of bone invasion. It suggested that certain humoral factor secreted by the tumor may contribute to the pathogenesis.We partially purified and characterized bone resorption factor (BRF) from human transitional cell carcinoma (TCC) , rat Walker 256 carcinoma and mouse 7,12 dimethyl benz (a) anthracene (DMBA) induced squamous carcinoma. Gel filtration chromatography of tumor extract demonstrates a single major peak of bone resorption activity (BRA, 45Ca release from calvarial bone) that elutes with an apparent MW of about 15,000 dalton. The BRA is associated with increased release of immunoreactive PGE 2 and both can be inhibited by indomethacin and boiling. In TCC and DMBA, the BRA were co-eluted with an activity of stimulating aden-ylate cyclase in rat osteosarcoma cells ROS 17/2.8. It appears that these factors are unique BRF, which are different from other known factors that can cause bone resorption.